5.1Why they aren’t optional
In the wild these animals eat plants and insects with a favourable calcium to phosphorus ratio. What we can buy tends to contain more phosphorus than calcium.
A dragon needs to hold 2 parts calcium to 1 part phosphorus in its bloodstream. When that slips, the body takes calcium out of its own bones to correct it. Over months the bones go soft, then weak, then rubbery.
That is metabolic bone disease, covered properly in 9.1. It’s the most common serious illness in pet bearded dragons and almost entirely preventable with correct UVB and correct dusting.
5.2The schedule
| Supplement | How often |
|---|---|
| Calcium without D3 | Most feedings, dust lightly on feeders and salad |
| Calcium with D3 | Once or twice a week |
| Multivitamin | Once every two weeks |
Dose is a pea-sized amount, on both salad and insects. Everything gets dusted. The one exception is greens you grew yourself without fertiliser.
On the D3 version: there’s an open debate about whether bearded dragons absorb dietary D3 at all, and the consensus is somewhere between a tiny amount and none. It won’t hurt them and it’s worth doing as insurance, but it is not a substitute for UVB. Your UVB does the real work.
5.3The three supplements and what each does
Three products cover everything a dusted diet needs to correct.
| Product | Specification |
|---|---|
| Calcium without D3 | Phosphorus-free calcium carbonate. It exists to correct the calcium-to-phosphorus ratio described in 5.1, so a product containing phosphorus works against its own purpose. Particle size matters practically, a fine powder adheres to feeders, a coarse one falls off. |
| Calcium with D3 | The same, plus cholecalciferol. Read the D3 figure and see 5.4, the range across products is enormous. |
| Multivitamin | Fills the gaps a captive diet leaves. The form of vitamin A matters: beta-carotene is converted by the body only as needed, whereas preformed retinol accumulates, so the former is much harder to over-supply. |
They are used on different schedules and at different frequencies for different reasons, which is why a single all-in-one dust cannot do the job of all three.
5.4How much D3 is in the jar
This is the number worth checking, because products that look interchangeable on the shelf are not. Across the calcium-with-D3 supplements on sale, D3 content ranges from around 4,400 to 400,000 IU/kg, a factor of about ninety, invisible from the front of the tub.[17]
Reading the panel
Two things trip people up.
Units differ. Most US labels state D3 per pound; European ones usually state it per kilogram, and some give it in milligrams of cholecalciferol instead. To compare like with like: multiply an IU/lb figure by 2.2 to get IU/kg, and multiply a mg/kg figure by 40,000 to get IU/kg.
Calcium and D3 sit on adjacent lines in very different units, and on at least one product the same numeral appears on both. A panel reading 40% calcium is also 400,000 mg/kg of calcium, which looks alarming next to a D3 figure in IU/kg. They are different substances measured different ways. For scale, even the highest D3 figure on the market works out to about 10 mg of cholecalciferol per kilogram of powder, roughly 0.001% by weight. There is no product where D3 is a bulk ingredient.
⚠ The “under 23,000” rule isn’t a standard
You will see it stated that a calcium-with-D3 product should sit under 23,000 IU/kg. We couldn’t find any veterinary or scientific source behind that number. It appears to have been drawn around what was already on the shelf rather than derived from any study of dose and response.
There is a second problem with treating a concentration as a safety limit. IU per kilogram is not the dose the animal gets. What actually reaches the dragon depends on how much powder sticks to the feeder and how much of the diet is dusted. A concentration on its own can’t establish an overdose risk.
So we’re not going to state it as a rule. What holds up is narrower and still useful: if your dragon has good UVB, it is already making the D3 it needs, and there is no benefit in choosing a high-D3 supplement on top of that. The lower end of the range is the sensible default, and it costs nothing to pick it. Products at the high end exist mainly for animals kept without UVB, which is not the situation this guide describes.
5.5Probiotics
A probiotic puts beneficial bacteria back into the gut, which helps digestion and keeps the bad bacteria in check. Reptile-specific probiotics are sold as powders and as gels, and both work.
Dosing the powder goes by weight rather than volume, one level teaspoon is roughly 2.7 g. Once or twice a week for maintenance. If you’re treating parasites, run it for 30 days.